1 files changed, 80 insertions, 0 deletions
diff --git a/tex/context/base/mkiv/buff-imp-nested.lua b/tex/context/base/mkiv/buff-imp-nested.lua
new file mode 100644
index 000000000..019cd996d
--- /dev/null
+++ b/tex/context/base/mkiv/buff-imp-nested.lua
@@ -0,0 +1,80 @@
+if not modules then modules = { } end modules ['buff-imp-nested'] = {
+    version   = 1.001,
+    comment   = "companion to buff-imp-nested.mkiv",
+    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
+    copyright = "PRAGMA ADE / ConTeXt Development Team",
+    license   = "see context related readme files"
+}
+
+local lpegmatch, patterns = lpeg.match, lpeg.patterns
+local P, V, Carg = lpeg.P, lpeg.V, lpeg.Carg
+
+local context       = context
+local verbatim      = context.verbatim
+local variables     = interfaces.variables
+
+local makepattern   = visualizers.makepattern
+local getvisualizer = visualizers.getvisualizer
+
+local nested = nil
+
+local donestedtypingstart = context.donestedtypingstart
+local donestedtypingstop  = context.donestedtypingstop
+
+local v_none    = variables.none
+local v_slanted = variables.slanted
+
+local handler = visualizers.newhandler {
+    initialize = function(settings)
+        local option = settings and settings.option
+        if not option or option == "" then
+            nested = nil
+        elseif option == v_slanted then
+            nested = nil
+        elseif option == v_none then
+            nested = nil
+        else
+            nested = getvisualizer(option,"direct")
+        end
+    end,
+    open = function()
+        donestedtypingstart()
+    end,
+    close = function()
+        donestedtypingstop()
+    end,
+    content = function(s)
+        if nested then
+            nested(s)
+        else
+            verbatim(s)
+        end
+    end,
+}
+
+local open  = P("<<")
+local close = P(">>")
+local rest  = (1 - open - close - patterns.space - patterns.newline)^1
+
+local grammar = visualizers.newgrammar("default", {
+
+    initialize = patterns.beginofstring * Carg(1) / handler.initialize,
+
+    open       = makepattern(handler,"open",open),
+    close      = makepattern(handler,"close",close),
+    rest       = makepattern(handler,"content",rest),
+
+    nested     = V("open") * (V("pattern")^0) * V("close"),
+    pattern    = V("line") + V("space") + V("nested") + V("rest"),
+
+    visualizer = V("initialize") * (V("pattern")^1)
+
+} )
+
+local parser = P(grammar)
+
+visualizers.register("nested", { parser = parser, handler = handler, grammar = grammar } )
+
+-- lpeg.match(parser,[[<<tf<<sl>>tf<<sl>>tf>>]]) context.par()
+-- lpeg.match(parser,[[<<tf<<sl<<tf>>sl>>tf>>]]) context.par()
+-- lpeg.match(parser,[[sl<<tf<<sl>>tf>>sl]])     context.par()